1. Field of the Invention
This invention relates to a fluorescence endoscopy and an endoscopic device therefor, by which, while irradiating a ray of exciting light to an object to be examined containing a fluorescent substance, information on fluorescence emitted by the object is obtained.
2. Related Art Statement
In recent years, an endoscope is in wide use as it can observe organs or the like in a venter by inserting a thin, long inserting portion in the venter, or it can make various treatments by inserting, as the case may require, various treatment tools into a treatment tool channel provided therein.
Many different types of electronic endoscopes using a solid state imaging device such as a charge coupled device (CCD) as imaging means have also been proposed.
As a method for examining organic conditions of man using the endoscope, there is a method for observing fluorescence by which, while giving a fluorescent substance to an object to be examined such as internal organs and irradiating a ray of exciting light to the object, a fluorescent image formed by fluorescence emitted by the fluorescent substance is observed, as disclosed, for example, in Japanese Patent Unexamined Publication No. 63-122421 or in U.S. Pat. No. 4,821,117.
However, the conventional method required a special light source for emitting the exciting light ray and special imaging means for observing the fluorescent image. Thus, in order to obtain both an ordinary image in the visible range and a fluorescent image, as disclosed in the Japanese Patent Unexamined Publication No. 63-122421 and in the U.S. Pat. No. 4,821,117, it was necessary to make a switching operation between the exciting light and the light for ordinary observation, and this made it difficult to observe a chronological change, for example, in fluorescence produced after a phleboclysis of the fluorescent substance has been made. The arrangement of the device was also complicated so as to obtain both the ordinary image in the visible range as well as in the fluorescent image.
Fluorescent substances such as fluorescein and adriamycin generally have their absorption range in the shorter wavelength side, whereas their fluorescence range is in the longer wavelenght side. Further, the endoscopic image is generally strong in the red wavelength. As a result, when trying to observe fluorescence simultaneously with the ordinary image, fluorescence emitted by the endoscopic object is buried in the endoscopic image, because fluorescence is in the longer wavelength side, or in other words, is close to red, thus the fluorescence has not been well identified.
In order to solve this problem, what is conceivable is to apply an enhancing process to a range of wavelengths of fluorescence. However, since fluorescence is close to red as described above, it is difficult to make a relative difference with respect to the original red part of the endoscopic object, and thus it is not possible to obtain a successful enhancing effect.